A limited range is one of the most common complaints that many people have concerning their voice.
The range needed to sing a song can vary greatly. Some songs are simple, and others are complex. One song may have a range of just a few notes (3 Blind Mice), another may stretch around an octave or 8 notes (Do-Re-Mi from Sound of Music), and others might stretch at least 2 octaves (Music of the Night from Phantom of the Opera).
So, one may be able to sing a simple song pretty easily, but as the song becomes more complicated, then one would need to be able to stretch and move over a wider range in order to sing the song. When a person wishes to be able to sing more notes or extend their range, then that person often has to seek out a knowledgeable voice teacher in order to be guided in exercises that will extend the vocal range in a healthy way.
Now, the first and primary goal of voice training is to train the vocal muscles to do their jobs and relate to one another in a friendly manner. As the vocal muscles work well, the range extends naturally. A person’s range should extend over 2 octaves with some individuals able to navigate a larger range.
To be sure, it is not enough to be able to squawk out notes over a wide range anyway you can. Rather, it is the goal of healthy vocal training to be able to sing a wide range with comfort and no strain. We do not want to just sing a mess of notes, limited range or not – but to sing a whole mess of notes healthily.
A basic way that the teacher can guide and train the singer in reaching the goal of a wider range is to sing exercises that work out each major muscle (the arytenoid system and the crico-thyroid system) specifically, and then have these muscles start to work together in one exercise.
You could think of it like counseling. Each person is counseled individually so that they are able to deal with their personal issues and to know what they bring to the table. Then the two people are brought together for joint counseling sessions wherein they learn how to be best friends! As these muscles become strengthened on their own, and learn how to be best friends with one another, then the range is extended. You can sing higher and lower with no stain and no pain.